I don't think it's illogical nor irrational. When you look at artworks below €5 000 then there should be correlation between artistic value and price in euros.

I don't think it's illogical nor irrational. When you look at artworks below €5 000 then there should be correlation between artistic value and price in euros. Not exactly a linear function, but clear correlation. Above that you're not buying artwork - you're buying the prestige and social status of owning an expensive artwork. It's the rich people's equivalent of buying Supreme clothes just to impress the ladies.